What makes an injector atomize?

Why don't you use an oil burner nozzle, they are cheap, and come in various gallons per hour ratings. Try 1 gallon for starters. You will need to supply

The hole in the nozzle is very fine, maybe on the order of .010", plus all the internal guts of the nozzle that produces the spray pattern.

or you can get an old Beckett burner......

Atomization can be accomplished just with high pressure thru a fine jet producing a high-velocity jet that "shatters" when it hits air, or with a lower velocity jet of liquid that is sheared by a transverse air flow. An example of the former is an airless paint sprayer, and perhaps the injectors in a diesel engine. (Comment from diesel experts please?)

Domestic oil burners use medium pressure oil shooting thru an orifice into air moving at 800 fpm or so. There was a lower-pressure fan-atomized burner being developed at Brookhaven Nat'l Labs about 5 years ago and in early stages of commercialization at that time.

Paint sprayguns aspirate liquid into a stream of air produced by a high-pressure (30 - 50 PSI) jet or lower pressure turbine (HVLP), producing a low-velocity or lower-velocity finely-atomized spray. Fog-generators (as industrial-strength mosquito foggers) produce a micron-sized aerosol with what amounts to a very HVLP process.

If the velocity of the air-fuel mix is lower than the flamefront propagation velocity, then you need a flameholder. Low pressure gas burners (as in a stove) work this way. Higher pressure burners like the Reil burner don't need a flameholder. IIRC, domestic oil burners (as Beckett) do have a flameholder, but I think in normal operation the flame front typically resides in front of the flameholder. The flow and counterflow of gasses in the combustion region of an oil burner is quite complex.

Oil burners can produce high levels of CO if not running right. Please have good ventilation and have a CO monitor when experimenting. "Blue flame" burners (oil or gas) tend to produce less CO but more NOx.

Fuel injectors from a car engine have a pintle valve seating in the orifice. The fuel sprays through an annular opening formed between the tip of the pintle and the orifice. I would imagine this helps atomization. And a common operating pressure, (this is for GM), is 46 psi. Kept constant across the injector by manifold vacuum acting on the fuel press. regulator.

Garrett Fulton

- I should add, why (physics behind it). What determines droplet size, etc.?

Tim

-- "I've got more trophies than Wayne Gretsky and the Pope combined!" - Homer Simpson Website @

Don,

It is difficult to make domestic oil burners produce CO. And when they do produce CO , there is eye tearing fumes and soot, so it is detectable.

On the other hand, natural gas/propane can produce undetectable CO, hence are more dangerous in enclosed spaces.

Tony

"Don Foreman" wrote: [atomization]

Great link. Some related trivia: larger raindrops aren't the classic teardrop shape, they look more like a sphere with the bottom pushed up. This can be seen as an early stage of the "bag and disintegrate" pneumatic atomization process described on the linked site.

Tim

Geez, I think the pressure is a LOT higher than that. I tore down an old Sunstrand oil burner pump, and it is a two stage hydraulic gear pump. When pressure builds up, a valve shifts to put the two gear pump stages in series. I would thing the pressure must be in the thousands of PSI to need two stages of positive displacement pump in series.

I thought Diesel engine injectors were supposed to deliver about 10,000 PSI at the nozzle, when running at the higher speeds.

Jon

That's right, with domestic burners used as designed and built. If a guy starts experimenting, though, it definitely is possible. CO is definitely detectable. One should always have a CO monitor when fooling around with burners in any way other than installing an unmodified factory burner in the way it was intended to be used.

Nope, oil burner pumps output at 100 psi, although newer burners are spec'd at 140~150 psi as they try to get better atomization. Oil burner nozzles are flow rated at 100 psi.

If you have a 2 stage pump you probably have a Sunstrand J pump. Two stage oilburner pumps are used in high vacuum situations, where oil needs to be pumped from a tank long distance or a large difference in elevation from the burner.

The more common pump style is a A or B pump, single stage which works on most situations.

Diesel eng> > Why don't you use an oil burner nozzle, they are cheap, and come in various

Some airless spray nozzles atomize by imparting a rotating velocity to the liquid before it's ejected from a tiny hole. The centrifugal forces blow it apart at exit. I imagine there are similar fuel nozzles. The device that rotates the fluid is immediately behind the exit orifice, and is a plate with tangential grooves that bring the liquid from the outside toward the center, with each groove offset from the centre like the vanes on a centrifugal pump rotor.

Dan

That's how any furnace nozzles that I have dismembered were built. Gerry :-)} London, Canada

velocity to

centrifugal

_reaction_ (not force)

blows it apart at exit. I imagine there are similar fuel

behind the

bring the

offset

What's that Lassie? You say that Tim Williams fell down the old rec.crafts.metalworking mine and will die if we don't mount a rescue by Fri, 10 Sep 2004 23:21:28 -0500:

I see two channels that impart some rotation inside windex-like spray nozzles. I think I remember seeing the same thing in an oil burner nozzle.